1. Field of the Invention
This invention relates to a system to remedy the effects of erosion, and in particular, a beach replenishment system.
2. Background of the Invention
Erosion is the process whereby earth or rock is worn away over time. This is a natural process which works slowly but surely. Over hundreds of thousands of years, mountains can be worn down until they are level with the surrounding plains. The earth's surface is constantly being changed by erosion.
The main causes of erosion are the action of the air (wind) and water. Rainfall, running water (such as exists in rivers and streams), ice and wind all wear away at earth and rock.
In a beach environment, wave action is the prime cause of beach erosion. The earth contains hundreds of thousands of miles of seacoasts which are reshaped every day by waves. These waves are caused by wind, the gravity of the sun and moon, and submarine earth tremors. Seacoasts are eroded by surging seas, and molded by the drifting sands carried by waves.
Wave power can be enormous when waves strike land. The worst coastal weather in the world is in the North Atlantic. Hydraulic engineers have measured the force of waves breaking on the Scottish coast at 6,000 pounds per square foot. At one point a sea storm tore apart a breakwater by ripping away a 800 ton concrete slab, together with the 550 ton foundation to which it was attached. A new 2,600 ton section was installed, only to be swept away by a subsequent storm.
Hurricanes are a prime cause of beach erosion in North America and the Caribbean. Recent hurricanes have caused extensive beach depletion in Florida, the Carolinas, Costa Rica, the U.S. Virgin Islands, and even Long Island, in New York State. Swimming beaches have disappeared entirely, and buildings have had their foundations washed away.
Therefore, it is a matter of urgent importance to replenish the beach in those areas which have suffered from beach depletion. Once a beach is built up again, the new sand serves as protection to the coastline against inevitable storms, is useful for recreation, and prevents buildings from being washed away by sea waves.
Existing Designs
A number of ideas have been advanced to prevent beach erosion, and to replenish beaches which have suffered from erosion depletion. U.S. Pat. Nos. 5,509,755, 4,784,520 and 4,669,913 were granted Olsen et al., Stevens, and Temple for barriers which were substantially triangular in cross-section. While these designs provided a valley behind a barrier in which to trap sand, they suffered from a number of drawbacks. None of these designs incorporated provisions to prevent sand under a barrier extreme or front from being washed away by wave action. In addition, none of these designs taught a plurality of terraces in which sand could accumulate to multiply the sand retained by the system. Finally, no means to direct sand-bearing water into the barriers was taught.
U.S. Pat. Nos. 5,405,217 and 4,966,491 were granted Dias et al. and Sample, respectively for erosion control devices which were capable of filling with sand, to help immobilize these barriers in the presence of waves. While both these designs provided a valley behind a barrier in which to trap sand, they also suffered from the same drawbacks as the previously mentioned designs. Neither of these designs incorporated provisions to prevent sand under a barrier extreme or front from being washed away by wave action. In addition, neither of these designs taught a plurality of terraces in which sand could accumulate to multiply the sand retained by the system. Finally, no means to direct sand-bearing water into the barriers was taught.
DeVries et al. was granted U.S. Pat. No. 5,022,784 for a system which protected shorelines by reducing undertow. The system required the installation of long underground pipes, and the protrusion of intake pipes into the surf zone. This system suffered from complexity, and expensive installation, because most of the underground pipe installation had to be performed underwater. In addition, the intake pipes presented a possible hazard to swimmers in the surf zone, who risked tripping over, or stepping in, the intake pipes.
Bestmann received U.S. Pat. No. 5,338,131 for a shoreline protection system which used plants to stabilize a shoreline. While it as a well-known fact that plants are capable of protecting shorelines and dunes from erosion, their use in a beach environment presents a number of problems. From an aesthetic point of view, sandy beaches are enjoyable to the beach-goer precisely because the beach is free from plants and bushes, and the beach-goer may relax on a beach made up of 100% clean white sand, free of the soil associated with plant growth. In addition, few if any plants are capable of surviving in salt water surf. Finally, even if the plant rolls immobilized by stakes taught by this patent were installable in salt water surf, they would present a hazard to swimmers who might trip over the plant rolls or step on the stakes.